CHST4 is an N-acetylglucosamine 6-O sulfotransferase. The encoded enzyme transfers sulfate from 3'phosphoadenosine 5'phospho-sulfate to the 6-hydroxyl group of N-acetylglucosamine on glycoproteins. This protein is localized to the Golgi and is involved in the modification of glycan structures on ligands of the lymphocyte homing receptor L-selectin.